JPH0566189A - Method and device for measuring electrical characteristics - Google Patents

Abstract

PURPOSE:To enable the electrical characteristics of a compound whose state is changed at the application of voltage to be measured by using a piezoelectric element as a detector, and measuring the resonance frequency and the resonance resistivity of the element. CONSTITUTION:On a piezoelectric element serving as a detector a sample is fixed in such a manner that voltage can be applied thereto and a pulse generator 2 and an impedance measuring apparatus 3 are connected to the respective portions of the sample. The resonance frequency and the resonance resistivity at the application of voltage to the sample are measured by the pulse generator 2 and the impedance measuring apparatus 3 whereby the state change of the sample at the application of voltage can be measured as change in viscoelasticity. Therefore, the electrical characteristics of a compound whose state is changed with voltage can be measured using a piezoelectric element as a detector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to chemistry, polymer chemistry,
And to a method and apparatus for testing / evaluating the electrical characteristics of a compound that undergoes a state change when a voltage is applied, in the field of electronics.

[0002]

2. Description of the Related Art Conventionally, as a method for evaluating the electrical characteristics of a liquid crystal compound, a sandwich structure cell in which a liquid crystal compound is sandwiched between two electrodes as shown in FIG. 2 has been used. This is a method of optically measuring the alignment state of a liquid crystal compound when a voltage is applied between two electrodes.

[0003]

However, in the conventional method using the sandwich type cell, a large amount of sample is required to construct the cell. In addition, since the electrical characteristics of the compound to be measured are detected by light, the substrate and electrodes of the cell must be transparent, and due to problems such as the absorption wavelength of the sample, the wavelength of the detection light must also be changed depending on the sample. There was a problem that it would not happen.

Therefore, the object of the present invention is to solve the above-mentioned conventional problems, and the electrical characteristics can be measured by detecting the viscoelastic change of a sample using a piezoelectric element.
To obtain a measuring method and device.

[0005]

In order to solve the above-mentioned problems, the present invention uses, for example, an AT-cut crystal oscillator as a detector, and continuously measures the resonance frequency change or impedance change of the crystal oscillator. This makes it possible to easily measure electrical characteristics with a very small amount of sample.

[0006]

The electrical characteristic measuring device configured as described above is
Although a piezoelectric element is used as a detector, this piezoelectric element causes mechanical vibration by applying a voltage having a frequency near the resonance frequency. This vibration is extremely small,
When the substances are in contact with each other, resistance due to shear stress between the substances and the surface of the piezoelectric element is applied. It can be considered that the resistance coefficient of the mechanical resistance is equivalent to the electric resistance when the mechanical vibration and the electric vibration of the piezoelectric element are considered in association with each other. Therefore, the resonance resistance at the resonance frequency is considered to be a value that reflects the friction coefficient of the surface of the piezoelectric element, and the viscoelastic change of the substance can be measured by continuously measuring this resonance resistance. Further, since the shear stress of the piezoelectric element balances with the force that vibrates as the elastic body of the piezoelectric element, the change in resonance frequency also corresponds to the change in viscoelasticity. Therefore, the viscoelastic change of the sample can be traced by measuring the change of the resonance frequency. Here, it is known that the resonance frequency of the piezoelectric element changes due to elasticity, viscosity, and weight change of the sample, and the resonance resistance changes only due to viscosity change. Therefore, when there is no weight change, the viscous change and elastic change of the sample can be considered by comparing the resonance frequency and the resonance resistance value.

On the other hand, it is known that when an electrical orientation change occurs in a sample, the viscoelasticity changes before and after the electrical change. Therefore, the electrical characteristics of the sample are measured by applying these two properties. It became possible to do. As the piezoelectric element, a SAW device, a piezoelectric ceramic oscillator, or the like can be used in addition to a crystal oscillator.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic diagram of an electric characteristic measuring apparatus of the present invention. In FIG. 1, an AT-cut crystal oscillator cell 1 is connected to a pulse generator 2 and an impedance measuring device 3 whose measurement frequency can be arbitrarily set.
The pulse generator 2 and the impedance measuring device 3 are connected to a computer 4 for further performing calculation or control, and a printer 5 is connected to the computer 4. 3 is a schematic diagram of the electrical characteristic measuring device of FIG.
1 shows a structure of a T-cut crystal oscillator cell 1 portion. The AT-cut crystal unit 11 is sealed with a silicone resin in a plastic holder 15 having a structure in which only one surface is in contact with the sample. Further, the AT-cut crystal oscillator 11 has a structure in which a voltage application electrode 14 to the sample is placed on the sample surface via a spacer 16. Then, the sample 6 enters the space surrounded by the AT-cut quartz crystal resonator 11, the voltage application electrode 14, and the spacer 16.

The common electrode 13 is used in combination with the voltage application electrode 14 to apply a voltage to the sample and at the same time in combination with the crystal oscillator electrode 12 to apply a voltage to the crystal oscillator. In the measuring method of the present invention, the sample is fixed on the AT-cut crystal oscillator 11, and a voltage is applied to the sample, and at the same time, the impedance near the resonance frequency of the AT-cut crystal oscillator 11 is continuously measured. The resonance frequency and the resonance resistance value of the AT-cut crystal unit 11 with respect to the voltage are obtained.

When the sample is fixed to the AT-cut crystal oscillator cell 1, the resonance frequency and the resonance resistance value of the AT-cut crystal oscillator 11 reflect the viscoelasticity of the sample at the applied voltage at the time of measurement, resulting in resonance. The frequency and the resonance resistance value are measured using the impedance measuring device 3. Figure 4
3 is a block diagram of the impedance measuring device used in this example. The signal generation unit 17 generates a frequency near the resonance frequency of the AT-cut crystal unit 11, and the signal distribution unit 18 distributes the signal obtained by the signal generation unit 17 into two. One of the signals divided into two enters the arithmetic unit 26 as it is via the amplification unit A19, the attenuator unit A20, and the logarithmic amplification unit A21. The other is AT-cut crystal unit 1
After passing through 1, the calculation unit 26 is entered through the amplification unit B22, the attenuator unit B23, and the logarithmic amplification unit B24. Further, the signal output from the attenuator section B23 passes through the AT-cut crystal unit 11 on the way, so the attenuator section A
There is a phase difference with the signal coming out of 20. This phase difference is detected by the phase difference detection unit 25 and input to the calculation unit 26. The computing unit 26 obtains the conductance and susceptance of the AT-cut crystal unit 11 from the input signal and displays it on the display unit 27.

In impedance measurement, specifically, since there is a resonance frequency between the frequency that gives the maximum value and the minimum value of the susceptance, which is the imaginary part of the admittance, first the maximum and minimum values of the susceptance are set to the frequency. The values were obtained by sweeping, and the conductance and susceptance were measured at evenly spaced frequencies.
For the measured values, conductance and susceptance data were processed by the method of least squares of a circle, and the diameter of the circle was obtained. Further, the center of the circle was obtained, and the frequency on the circle showing the same susceptance value as the value of the susceptance at this center point was obtained from the polynomial approximation of the susceptance and the measurement frequency, and this was used as the resonance frequency.

The computer 4 performs the processing of the impedance measurement and the calculation for obtaining the resonance resistance value and the resonance frequency.
Automatically, and the result is displayed and printed on the display and the printer 5. Further, in the present embodiment, the AT-cut crystal unit was used as the detector, but the same measurement can be performed using a GT-cut crystal unit or another piezoelectric material such as a SAW device or a piezoelectric ceramic oscillator. Has been shown.

Next, the result of measurement using this measuring method and apparatus will be described. As a sample, a cyanobiphenyl-based liquid crystal compound (E44 manufactured by Merck & Co., Inc.), which is generally used for display devices and the like, was used. 5V 0.1H
When the voltage of z was applied, the resonance frequency and the resonance resistance value changed due to ON-OFF of the voltage. From this, it was confirmed that the electrical property measuring device of the present invention can measure the change in the orientation state of the compound due to the voltage.

The present invention can be widely applied not only to the above embodiment but also to, for example, measurement of the separation process of organic compounds by electrophoresis.

[0015]

As described above, according to the present invention, the state change of the sample is measured from the change of the resonance frequency and the resonance resistance value of the piezoelectric element when the voltage is applied to the sample. In addition, there is an effect that the electrical characteristics of a compound that changes its state with voltage can be measured without constructing a complicated and labor-intensive measurement system like the conventional one.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an electric characteristic measuring device of the present invention.

FIG. 2 is an explanatory diagram of a conventional sandwich structure cell for measuring electrical characteristics.

FIG. 3 is an explanatory diagram showing a structure of an AT-cut crystal oscillator cell used in an example of the present invention.

FIG. 4 is a block diagram of an impedance measuring device used in an example of the present invention.

[Explanation of symbols]

 1 AT-cut crystal oscillator cell 2 Pulse generator 3 Impedance measuring device 4 Computer 5 Printer 6 Sample 7 Glass substrate 8 Transparent electrode 9 Polarizer 10 Detection light 11 AT-cut crystal oscillator 12 Crystal oscillator electrode 13 Shared electrode 14 Voltage Application electrode 15 Holder 16 Spacer 17 Signal generator 18 Signal distributor 19 Amplifier A 20 Attenuator A 21 Logarithmic amplifier A 22 Amplifier B 23 Attenuator B 24 Logarithmic amplifier B 25 Phase difference detector 26 Arithmetic unit 27 Display

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuhiko Kimura 6-31-1, Kameido, Koto-ku, Tokyo Seiko Denshi Kogyo Co., Ltd.

Claims (2)

[Claims] 1. A piezoelectric element is brought into contact with at least one surface thereof, and when a voltage is applied to the sample, a resonance frequency or a resonance resistance value of the piezoelectric element is measured to detect a viscoelastic change of the sample. A method for measuring electrical characteristics, which comprises measuring the electrical characteristics of a sample that changes state when a voltage is applied. 2. A device for measuring at least a piezoelectric element and a resonance frequency of the piezoelectric device, or a device for measuring a resonance resistance value of the piezoelectric device, and one surface of the piezoelectric device is brought into contact with the sample, and the piezoelectric device in contact with the sample. The sample holding part has an electrode and an electrode placed in parallel with the electrode sandwiching the sample, and continuously measures the resonance frequency or the resonance resistance value of the piezoelectric element when a voltage is applied between the both electrodes. An electrical characteristic measuring device is characterized in that the electrical characteristic of the sample that causes a state change when a voltage is applied is measured by detecting the viscoelastic change of the sample.